(a) Field of the Invention
The present invention relates generally to combined flywheel energy storage and attitude control systems for spacecraft. More particularly, it relates to a combined flywheel energy and attitude control system having both gimbaled and non-gimbaled flywheel pairs.
(b) Description of Related Art
The use of flywheels to provide energy storage on board spacecrafts is well known in the art. Recent advances in materials and electronics have increased the available specific energy of flywheel energy storage (FES) systems beyond that of electrochemical batteries, which have traditionally been used to store energy on board spacecrafts. Unlike electrochemical energy storage systems, energy storage and retrieval utilizing a flywheel system affects the attitude steering and momentum control of the spacecraft. Therefore, it is desirable to integrate the control of attitude steering and momentum management with the control of energy storage in the flywheel system of the spacecraft.
Combined FES and attitude control systems are also known in the art. For example, an exemplary combined FES and attitude control system is disclosed in U.S. Pat. No. 5,611,505 to Smay. Typically, these combined systems use counter-rotating pairs of flywheels that are gimbaled on two axes. However, for the emerging market of high power spacecraft, the number of flywheels (i.e., momentum) needed for energy storage far exceeds that required for attitude control. As a result, in these high-power applications one or more of the flywheel pairs do not have to be actuated for attitude control purposes, making their associated gimbaling hardware unnecessary.